The present invention relates to the method for advanced wastewater treatment using up & down aerobic-anaerobic reactors of channel type in the single reaction tank having the effluent recycle of channel type aeration reactor (internal cycle). More particularly, the channel type aeration reactor is composed of the aerobic state and the anoxic state according to the air diffusers.
The removal of nitrogen and phosphorus by using anaerobic and aerobic microorganisms under an anaerobic, an aerobic, and an anoxic condition is accomplished.
Recently, there is a problem that a damage due to the deterioration of water quality condition including an eutrophication, the red tide phenomenon etc, rapidly increases. The advanced wastewater treatment methods, at the same time, for removing the nitrogen and the phosphorus have been very much studied.
Especially, in the denitrification process, the aeration tank for oxidizing the ammonium nitrogen and the anoxic tank for returning the nitrate nitrogen to the nitrogen gas certainly are needed. And the volume of the reactor, in the case of combined removal of nitrogen and phosphorus by biological methods, is very much required because it is necessary to form the anaerobic tank for the phosphorus release and the aeration tank for luxury uptake of phosphorus, and these processes spatially have to be divided.
The most commonly used processes for combined nitrogen and phosphorus removal are the A2/O process, the five-stage Bardenpho process, the UCT process, and the VIP process. The sequencing batch reactor is also used for the combined nitrogen and phosphorus removal. The A2/O process is a modification of the A/O process and provides an anoxic zone for denitrification. The disadvantages of A2/O process are that performance under cold weather operating conditions are uncertain, and the operation is more complex than A/O.
The five-stage Bardenpho process modified the four-stage Bardenpho process for combined nitrogen and phosphorus removal. The staging sequence and recycle method are different from the A2/O process. The process uses a longer solids retention time than the A2/O process, which increases the carbon oxidation capability. The disadvantages of the five-stage Bardenpho process are that large internal cycle increases pumping energy and maintenance requirements.
The UCT process, developed at the University of Cape Town, is similar to the A2/O process with two exceptions. The return activated sludge is recycled to the anoxic stage instead of the aeration stage, and the internal cycle is from the anoxic stage to the anaerobic stage. The disadvantages of the UCT process are that large internal cycle increases pumping energy and maintenance requirements.
The VIP process (named for the Virginia Initiative Plant in Norfolk, Va.) is similar to the A2/O and UCT processes except for the methods used for recycle systems. The return activated sludge is discharged to the inlet of the anoxic zone along with nitrified recycle from the aerobic zone. The mixed liquor from the anoxic zone is returned to the head end of the anaerobic zone. The disadvantages of the VIP process are that large internal cycle increases pumping energy and maintenance requirements.
The sequencing batch reactor can be operated to achieve of the combined nitrogen and phosphorus removal. The disadvantage of the sequencing batch reactor is suitable only for smaller flows.